Metal working machine



1953 w. M. WOODWARD 2,845,751

METAL WORKING MACHINE 10 Sheets-Sheet 1 Filed Jan. 10, 1955 INVENTOR. WILL/4M M Wooowma ATTOANEVS Aug. 5, 1958 w. M. WOODWARD 2,845,751

METAL WORKING MACHINE 1O Sheets-Sheet 2 Filed Jan. 10, 1955 INVENTOR. WILL/AM M WoooWMo BY flm 10 Sheets-Sheet 3 0 n R4 J w w 3 l m 3 3 w QMJAW. M N H MN m 9 i t p l. \l Y 4 KN BM II III! I N5 N Aug. 5, 1958 w. M. WOODWARD METAL WORKING MACHINE Filed Jan. 10, 1955 l l l I I I l I I I IH 10 SheetsSheet 4 Aug. 5, 1958 w. M. WOODWARD METAL WORKING MACHINE Filed Jan. 10, 1955 i q A L w m% w%\ m r/// A \III g m flhu 1958 w. M. WOODWARD 2,845,751

METAL WORKING MACHINE 1O Sheets-Sheet 5 Filed Jan. 10, 1955 Am i P w LE: E

.mw w mu m m M W p I 0 M n M ,4 u a m 6 M M2 w Mz 2 M m z Aug. 5, 1958 w. M. WOODWARD METAL WORKING MACHINE 10 Sheets-Sheet 6 Filed Jan. 10, 1955 INVENTOR. WALL/4M M Moan M0 BY v Allg- 1958 w. M. WOODWARD 2,845,751

METAL WORKING MACHINE 1O Sheets-Sheet 7 Filed Jan. 10, 1955 INVENTOR. MLL/AM M. Mom/4R0 A flop/VH5 g- 1958 w M. wooDwARn 2,845,751

\METAL WORKING MACHINE 1O Sheets-Sheet 8 Filed Jan. 10, 1955 INVEN TOR. BY H mz IAN M 14 000140 u 1958 w. M. WOODWARD 2,845,751

METAL WORKING MACHINE Filed Jan. 10, 1955 10 Sheets-Sheet 9 INVEN TOR. H/Iu/AM M. boommo United States Patent lVlETAL WORKING MACHINE William M. Woodward, Birmingham, Mich., assignor to Mid-West Abrasive Company, Owosso, Mich., a corpor'ation of Delaware Application January 10, 1955, Serial No. 480,661

22 Claims. (Cl. 51-32) This invention relates to a metal working machine and more particularly to a swing grinder of the type commonly used for grinding metal billets of substantial length.

One object of this invention is to provide a grinding machine having a carriage movable along a track and a boom mounted on the carriage with an abrasive wheel rotatably mounted on the free end of the boom. The boom is supported by the carriage for vertical swinging movement and is slidable along its longtudinal axis to feed the abrasive wheel across a work piece. The boom is also rotatable in Opposite directions about its longitudinal axis to tilt the abrasive wheel in opposite directions.

Another object of the invention is to provide a construction wherein the abrasive wheel is automatically tilted in opposite directions during the grinding operation to maintain the wheel in a properly dressed condition.

Still another object of the invention is to provide counterbalancing means for the boom and associated parts including the brasive wheel, movable in opposed relation to the in and out axial sliding movement of the boom.

Still another object of the invention is to provide a variable pull down device for maintaining a predetermined downward pull upon the outer end of the 'boom which varies in accordance with the axial in and out movement of the boom. It is necessary to maintain a uniform grinding pressure of the wheel upon the work piece as it moves back and forth across the work piece. However, it has been found to be very difiicult if not impossible to accurately counterbalance the boom with weights alone. Accordingly, the pull down device of the present invention cooperates with the counterbalancing means to provide a uniform grinding pressure as the wheel moves back and forth across the work.

It has also been found that under operating conditions the engagement of the grinding Wheel with the work piece has a tendency to cause the wheel to chatter and the boom to vibrate in a vertical plane, particularly in the outermost position of the boom, if the boom is not subjected to sufficient hold down pressure. Although the boom may be counterbalanced in a manner to be slightly tool heavy, still there is this tendency toward chattering Where there is no positive or nearly positive resistance to upward swinging of the tool end of the boom. This can be appreciated when one pictures a rather massive boom more or less in balance with respect to the pivot axis. Clearly there is no positive resistance to vertical rocking. The pull down device of the present invention is in the form of a hydraulic fluid pressure operated piston cylinder assembly and adds a certain amount of downward pull on the tool end of the boom. In addition to the actual pull down pressure thus applied, the hydraulic fluid in the pull down assembly provides a much greater positive resistance against upward swinging of the boom. Even pneumatic pressure is useful for this purpose although it does not provide a resistance to chattering of the efiectiveness of hydraulic fiuid.

Other objects of the invention will become apparent 2,845,751 Patented Aug. 5, 1958 ice as the following description proceeds, especially when taken in conjunction with the accompanying drawings wherein:

Figure l is a top plan view of a metal working machine constructed in accordance with the present invention;

Figure 2 is a side elevational view of the machine shown in Figure 1;

Figure 3 is a sectional view taken along'the line 3-3 on Figure 1;

Figure 4 is a sectional view taken along the line 44 on Figure 3;

Figure 5 is a sectional view taken along the line 55 on Figure l;

Figure 6 is a sectional view taken along the line 6-6 on Figure 3;

Figure 7 is a sectional view taken along the line 77 on Figure 1;

Figure 8 is a front elevational view of the machine partly in section;

Figure 9 is a plan view of a portion of the boom, showing also the means connecting to the boom the motor for driving the abrasive wheel for in and out axial sliding movement as a unit with the boom;

Figure 10 is an enlarged view partly in section of a portion of the structure shown in Figure 9;

Figure 11 is an enlarged view partly in section of another portion of the structure shown in Figure 9;

Figure 12 is a sectional view illustrating the counterbalancing means for the boom;

Figure 13 is a sectional View taken along the line 1313 on Figure 1;

Figure 14 is a sectional view taken along the line 14-14 on Figure 3;

Figure 15 is a diagrammatic view of the hydraulic system; and

Figure 16 is a detail view of the pressure regulating valve.

The metal removing machine selected for the purpose of illustrating the present invention is adapted to remove metal by an abrading action and comprises a swing grinder.

7 Referring now more particularly to the drawings and especially to Figures 2, 3 and 8, it will be noted that the swing grinder has a supporting structure-which includes a track 10 and a carriage 12 supported thereon for movement in opposite directions along the track. The track comprises laterally spaced rails 14 and 16 suitable anchored to flooring or other supporting means not shown herein. The rail 14 is generally I-shaped in cross section and the rail 16 has an inverted channel-shaped cross section.

The numeral 18 designates a work support for a work piece W to be operated upon by the machine. In the present instance, the work piece may be considered as a metal billet of a substantial length, and it is the purpose of this machine to remove metal from the top surface of the billet. The track extends in the general direction of length of the billet so that the machine may move lengthwise of the billet during the grinding operation.

The carriage includes a rectangular platform 20 having downwardly extending flanges 22 at the front and rear ends of the platform, and the wheel supporting axles 24 and 26 are respectively journalled in the flanges 22. These axles extend from front to rear of the carriage and have wheels 28 and 30 keyed or otherwise secured to the opposite end portions of the axles in positions to engage the rails 14 and 16.

It will be noted that the wheels 28 which engage the track 14 have a circumferentially grooved periphery for engaging the track and guiding movement of the carriage therealong.

In the present instance, the carriage is driven in op- 3 posite directions along the track by a reversible fluid motor 32 of any suitable construction secured to the platform 20 of the carriage. The drive shaft of the motor is connected to a gear box 34 which has a sprocket 36 connected bya chain 38 to a sprocket 40 on the axle 24 to move the carriage in opposite directions along the track.

The fluid motor 32 is driven in a manner more fully described hereinafter. Briefly, as shown in Figure 15 of the drawings, the motor 32 is connected to fluid pressure supplied by a duplex pump assembly 37 and is selectively operated by a suitable four-way three position valve 39. The valve 39 is supported on the frame structure and is controlled by a lever 41.

The numeral 42 indicates a boom assembly which is mounted on the carriage 12 and which extends outwardly from the carriage at right angles to the track over the top of the work piece W, as shown in Figure 3 of the drawings. boom tube 44 supported on the carriage in a manner more fully described hereinafter and having an abrasive wheel assembly 46 mounted on the outer end thereof.

The abrasive wheel assembly 46 is shown in Figure 10 of the drawings as having a housing 48 formed with a circular recess 50 in the inner end wall thereof for receiving the outer end of the boom tube 44. The outer end of the boom tube is secured in the recess in any suitable manner and accordingly the abrasive wheel assembly is movable as a unit with the boom tube. One side of the housing 48 is open and is normally closed by a cover 52 having the inner edge pivoted to the housing by a pin 54 in a manner to permit outward swinging movement of the cover relative to the housing.

The wall 56 of the housing 48 opposite to the cover 52 is fashioned to support a spindle 58 with its axis extending at right angles to the axis of the boom tube 44. In detail, the Wall 56 of the housing is fashioned with a sleeve part 60 for receiving one end of the spindle 58 and the latter is secured to the sleeve part by a key 62. The spindle 58 extends from the sleeve part axially through housing 48 and the central portion of cover 52 is apertured to receive the free end of the spindle. It will be noted from Figure 10 that the free end of the spindle is threaded and the central portion of cover 52 is clamped to the spindle by a nut 64. A pulley 66 is journalled on spindle 58 by a roller bearing 68 and the periphery of the pulley is formed with axially spaced annular belt receiving grooves 70. The end of the pulley opposite the grooved end is secured by studs 72 to the adjacent end of a ring 74 having a reduced part concentric to the spindle 58 and journalled on the spindle by a roller bearing 76.

An abrasive wheel 78 is sleeved on the reduced portion of ring 74 and is seated against the shoulder 80 formed by the reduced portion of the ring. The abrasive wheel 78 is secured in place on the ring by an annular nut 82 which is threaded on the end of ring 74. An annular spacer 84 is supported on the ring between nut 82 and the abrasive wheel 78. With the above construction, the spindle 58 and associated parts may be readily installed or replaced when desired. The abrasive wheel may be replaced by merely swinging cover 52 to its open position and removing the clamping nut 82. As seen in Figure 3 of the drawings, the bottom of the housing 48 is open and the abrasive wheel 78 projects therebeneath for engagement with the work piece.

The abrasive wheel 78 is rotated by an electric motor 86 mounted on a carriage 88, which, in turn, is supported by a track 90 having laterally spaced rails 92 extending parallel to the axis of the boom tube 44. As shown par ticu-larly in Figure 8, the carriage is equipped with axles 94 having rollers 95 positioned at opposite ends thereof for rolling engagement with the respective rails 92. The carriage 88 is held in position on the track 90 by suitable brackets 96 secured to opposite sides of the carriage and having rollers 98 at'the lower ends thereof respectively The boom assembly 42 includes an elongated 4 A engageable with the bottom sides of rails 92. Thus, the carriage 88 with the motor 86 thereon is movable in the direction of the boom axis and at right angles to the track 10 between the broken and full line positio'ns shown in Figures 1 and 2 of the drawings.

The drive shaft of the electric motor 86 is connected to a gear box generally indicated at 100 suitably mounted on the carriage 88, and a pulley 102 is secured to the output shaft of the gear box. The pulley 102 has axially spaced grooves extending about the periphery thereof for receiving the inner ends of belts 104. The outer ends of the belts 104 are respectively received in the grooves 70 of the pulley 66 so that rotation of the motor 86 imparts a rotative movement to the abrasive wheel 78.

As will be described more fully hereinafter, the boom tube 44 is movable in opposite directions along its longitudinal axis in order to feed the abrasive wheel 78 back and forth across the work piece W. The carriage 88 is movable as a unit with the boom tube 44 during the feed ing traverse of the abrasive wheel. In order to accomplish this result, a tie rod assembly 106 is provided between the carriage 88 and the abrasive wheel housing 48. The tie rod assembly 106 comprises a plurality of axially aligned relatively movable parts and performs the additional functions of maintaining the belts 104 under the proper tension.

Referring now to Figure 11 of the drawings, it will be noted that the tie rod assembly 106 has a pair of central rod sections 108 suitably fashioned at the adjacent ends to overlie and interlock with one another. The rod sections 108 are held in their assembled relationship by a sleeve 110 normally extending over the joint between the overlying rod sections and frictionally held by a detent 112 against a stop in the form of a tapered pin 114. The sleeve 110 is movable axially of the tie rod assembly 106 in a direction away from stop 114 to enable disengaging the adjacent ends of rod sections 108 and thereby to permit replacing belts 104 when desired.

The axially outer ends of rod sections 108 are formed with recesses 116 for respectively receiving the inner ends of coil springs 118. The axially outer end of one of the coil springs 118 extends into a recess 120 formed in a part 122 which is secured to a bracket 124 rigidly carried by the gear box 100 on the carriage 88. The outer end of other coil spring 118 extends into a recess 126 formed in the axially inner end of a part 128. The axially outer end 129 of the part 128 is externally threaded and projects into a bore 130 formed in the housing 48. The bore 130 loosely receives the threaded end 129 of part 128 and a key (not shown) is employed to prevent relative rotation between the end 129 and bore 130.

In order to axially move the part 128 to adjust the tension on belts 104, a feed nut 132 is threaded to the part 129 and is arranged to mesh with a worm 134 suitably journalled in the housing 48. The arrangement is such that rotation of worm 134 imparts a rotative movement to the feed nut 132 which, in turn, axially shifts the threaded part 128 to effect the desired adjustment.

The parts 122 and 128 are respectively encircled by coil springs 136 having the convolutions adjacent the outer ends respectively engaged in helical grooves formed in the aforesaid parts and having the convolutions adjacent the inner ends thereof respectively lying in helical grooves formed in the rod sections 108. The coil springs 136 are under tension and the extremities thereof may be tack welded in place to provide the necessary tie between the parts 122 and 128 of the tie rod assembly.

The boom assembly 42 includes, in addition to the boom tube 44, an elongated housing 138 for the boom tube. The boom tube 44 is movable relative to the housing in the direction of its longitudinal axis to feed the abrasive wheel 78 back and forth across the work piece W. Suitably secured, within the housing 138 adjacent the inner end thereof is a sleeve 140having a bearing 142- secured withinthe sleeve 140. (see Figure 7). The outer end of the bearing 142 abuts an internal shoulder on the sleeve, and is clamped there against by an annular disc 144. Thebearing 142 supports the inner end portion of the boom tube both. for axial slidingmovement and for rotation.

Referring now to Figure 5, the. outer end portion of the housing 138 has securedtherein a sleeve 146 and secured within the sleeve is abearing 148. The inner end of the bearing 148 abuts an internal shoulder on sleeve 146 and a plate 150 is secured to the outer end of sleeve 146 by bolts 152, thereby confining and clamping the bearing 148 against axial shifting movement. The bearing 148 supports the outer end.portion of the boom both for axial sliding movement and for rotation.

The. boom tube 44 is reciprocated in the direction of its longitudinal axis relative to the housing 138 by a motor in the form of a double acting hydraulic piston cylinder assembly 154. Opposite ends of the cylinder 156 of the assembly 154 are secured to the under side of the housing 138 at longitudinally spaced points and a piston rod 158 secured to the piston of the assembly 154 extends beyond, the inner end of the assembly and is pivotally connected to a clamp 160 by means of a transversely extending pin 162 (see Figure 7). The clamp comprises upper and lower clamping parts 164 and 166 which cooperate to encircle the reduced inner end portion 165 of boom tube 44 in a manner permitting rotation of the boom; relative to the clamp. It will be apparent that inward and outward reciprocation of the piston of the hydraulic assembly 154 will result in a corresponding movement of the boom tube 44 relative to housing 138.

The assembly 154 is operated in a manner more fully described hereinafter. Briefly, as shown in Figure 15, the assembly is connected to fluid pressure supplied by a duplex pump assembly 37 and is selectively operated by a suitable four-way three position valve 170 mounted on the carriage frame structure. Valve 170 is controlled by a control element 171.

The boom assembly 42 is mounted upon the carriage 12 for swinging in a vertical plane in order to move the abrasive wheel into and out of engagement with the work piece W. Referring now particularly to Figure 6. it will be noted that the housing 138 has secured therewithin a block 172 which is provided with a central through passage for loosely accommodating the boom tube 44. Projecting laterally from opposite sides of the block 172 through openings in the side of housing 138 are trunnions 174 and the latter are respectively journalled in roller bearings 176 supported by the base of the U-shaped part 178 and the bracket 180 respectively. The U-shaped part 178 and the bracket 180 are secured to a part 182 of the carriage structure by bolts 184. The arrangement is such as to permit vertical swinging move ment of the boom assembly 42.

Referring now to Figures 4 and 5, it will be noted that four pairs of rollers 186 are respectively journalled on the plate 150 at opposite sides thereof in positions to engage laterally spaced vertically extending guide members 188. The guide members 188 are portions of a frame 189 secured to a part 190 mounted on the carriage 12. It follows from the foregoing that the boom assembly 42 is accurately guided throughout its vertical swinging movement about the pivot axes of trunnions 174.

A counterbalancing weight 192 is provided for the boom assembly 42 which is movable along the axis of the boom in opposed relation to the in and out sliding movement of the boom. The counterweight 192 operates to reduce the pressure of the grinding wheel on the work. Referring to Figures 3 and 12, it will be noted that a housing extension 194 is provided at the inner end of the boom; housing 138. The counterweight 192 is rea ciprocable within the housing extension 194. in the direction of the boom tube axis. Suitably secured within the upper portion of the housing extension 194 are a pair of channel-shaped rails 196* which are disposed in laterally spaced relation and which open laterally outwardly. These rails 196 extend parallel to the axis of the boom tube 44. A pair of hangers 198.respectively have their lower ends secured to the counterweight 192 and have rollers 200 at their upper ends positioned to have rolling engagement with the lower flanges 202 of the rails 196', enabling the reciprocation of the counterweight in the direction of the boom tube axis.

Fixedly secured to the base of each channel-shaped rail 196 at points adjacent opposite ends thereof are the depending brackets 204. The brackets 204 adjacent the outer end of the housing extension 194 are arranged in laterally opposed relation and respectively rotatably support the opposite ends of a shaft 206 to which is secured a centrally disposed sprocket 208. The brackets 204 at the inner end of housing extension 194 also are arranged in laterally opposed relationship and rotatably support the opposite ends of a shaft 206 also having a centrally disposed sprocket 208 secured thereto. A chain 210 extends around the sprockets 208. Referring to Figure 7, it will be noted that the clamp 160 has a depending projection 212 which is secured to the upper run of chain 210.

Referring again to Figures 3 and 12, it will be noted that each shaft 206 has secured thereon a pair of sprockets 214 at opposite sides of the intermediate sprocket 208. Chain 216 extends around the sprockets 214 of each shaft at one side of sprocket 208 and chain 218 extends around the sprockets 214 at the other side of the shaft. The counterweight 192 is formed with the upwardly extending projections 220 which are respectively secured to the.

chains 216 and 218. As a result of this construction, the counterweight 192 will be moved in directions opposite to the direction of movement of the boom tube 44 so that the grinding pressure of the wheel on the work piece is reduced. However, as pointed out above, while it is necessary to obtain a uniform grinding pressure ofthe wheel upon the work as the boom moves along its axis, it is not feasible to accurately counterbalance the boom to obtain this result by weights alone. This will be appreciated when it is considered that a number of other assemblies move with respect to the boom pivot axis during axial sliding of the boom, such as the hydraulic motors and the electric motor for the abrasive wheel. In order to accurately counterbalance the boom, a hold down mechanism is employed which will be described below.

As pointed out above, the boom tube housing 138, together with the boom tube 44 may be swung vertically about the axis of trunnions 174. This is accomplished by a motor in the form of a double acting hydraulic piston cylinder assembly 222, the cylinder 224 of which is pivoted to the carriage 12 for rotation about the axis of pivot pin 226 (see Fig. 8). The assembly 222 is disposed generally vertically beneath the boom assembly outwardly of the pivotal mounting for the boom assembly and the piston of the fluid motor has a piston rod 228 projecting from the piston of the assembly 222 which extends upwardly through the top of cylinder 224 and is pivoted to the bottom of plate by a pin 230.

As will be more fully described hereinafter, the piston of assembly 222 is moved in opposite directions in cylinder 224 by fluid under pressure supplied by the duplex pump assembly 37. The flow of fluid under pressure to cylinder 224 is controlled by a manually operated four way two position valve 232 mounted on the carriage and controlled by a control element 233.

It is often desirable to tilt or oscillate the boom in opposite directions about its axis. One purpose of this is to maintain the wheel in properly dressed condition. This may be accomplished by rotation of the boom 44 in the bearings 142 and 148. As seen in Figure 7, a sleeve 234 having an internal bore of uniform non-circular (in this instance square) cross section is secured in the inner end of boom tube 44. Extending into the noncircular bore of sleeve 234 is a rod 236 of like non-circular cross section throughout its length. The rod has its reduced and threaded inner end projecting freely through channel bracket 238 fixed to housing extension 194. Washer 240 is interposed between the shoulder 241 on rod 236 and plate 242 secured to bracket 238, and washer 244 is interposed between nuts 246 threaded on the end of rod 236 and plate 248 secured to the bracket. As a result, the rod is supported by the bracket in a manner preventing axial sliding but permitting rotation of the rod.

The rod 236 is slidable in the bore of sleeve 234, and is rotated by an arm 250 secured to the rod and projecting upwardly therefrom through an opening 252 in the top of housing extension 194. Rotation of arm 250 correspondingly rotates the rod.

As. shown in Figures 13 and 14 the radially outer end of arm 250 is formed with a radially extending slot 254 and a roller 256 is slidably supported in the slot. The roller is mounted on a driving member 258 which in turn is secured to the power output shaft of a speed reducer 260. The speed reducer is connected by a pulley 262 and belt 264 to an electric motor 266. The motor 266' and speed reducer 260 are secured to the top of housing extension 194. Roller 256 is eccentrically located with respect to the axis of rotation of driving member 258 so that the arm 250 is rocked in opposite directions in response to rotation of the driving member. The boom may thus be oscillated by rod 236 irrespective of the axial position of the boom with respect to the rod.

The electric motor 266 may be suitably connected in an electric circuit for convenient control by an operator on the carriage. A suitable wiring circuit and control therefor are shown in the application of Anthony A. Muehling Serial No. 345,484 filed March 30, 1953.

Referring to the diagram in Figure 15 it will be noted that the duplex pump assembly 37 comprises three pumps 270, 271 and 272 driven by an electric motor (not shown). The pumps 270 and 271 are of the rotary blade type and the intake sides thereof are connected by a conduit 274 to a reservoir 275. The reservoir contains a supply of hydraulic fluid and is suitably supported on the carriage.

The delivery side of pump 270 is connected through a relief valve 276 to the intake port 2A of valve 39. The intake port 2A in position 1 of valve 39 is connected to port A of the valve which is connected to the reservoir 275 by a conduit indicated by the, broken line 277. The ports 3A and 4A of valve 39 are closed in position 1 so that fluid under pressure from pump 270 is bypassed back to the reservoir. In position 2 of valve 39, fluid is delivered to the motor from port 4A through conduit 278 and flows from the motor back to the reservoir through conduit 279 and port 3A. In position 3, the motor is driven in the reverse direction from that of position 2. i

The intake side of gear pump 272 is connected to the reservoir by a conduit 280 and the delivery side of the pump is connected through a relief valve 281 to the intake port 2C of valve 170. In position 1 of valve 170, the intake port 2C is connected by port 50 to the return line 277 to the reservoir. The ports 36 and 4C are closed in position 1 so that fluid under pressure from the pump 272 is returned to the reservoir. It will be apparent that in position 2 of valve 170 the boom will be moved inwardly along its axis because the intake port 2C is connected to port 4C which is connected to the head end of assembly 154 by conduit 282 and fluid at the rod end is exhausted through conduit 283 to the port 3C communicating with exhaust port 50.

The intake side of the pump 271 is connected to the reservoir by the conduit 274 and the delivery side of the pump is connected through a relief valve 284 to the intake port 2B of valve 232. In position I of valve 232, port 2B is connected'to port 3B and the latter is connected to the piston cylinder assembly 222 above the piston thereof by a conduit 285, a pressure regulating valve 286 which will be more fully described hereinafter, and a conduit 287. It will also be noted in position 1 of valve 232 the assembly 222 below the piston is connected to port 413 of the valve by a conduit 288, the port 43 communicating with the port 5B which returns the fluid to the reservoir through the return line 277. Thus in the Figure 1 position of valve 232, the boom 44 will be lowered.

The boom will be raised in the No. 2 position of valve 232 as is readily apparent.

The pressure regulating valve 286 is shown in Figures 2, 15 and 16. This valve is provided to determine and regulate the pressure of fluid delivered to the pistoncylinder assembly 222 in position 1 of valve 232 urging the boom in a downward direction. Referring particularly to Figure 16, it will be seen that valve 286 comprises a casing 290 and the conduits 285 and 287 extend into the casing and communicate with each other at their junction with the longitudinally extending bore 291. The bore 291 extends entirely through casing 290 and has a needle valve element 292 therein. The valve element 292 has one end tapered to a point and adapted to seat in the frusto-conical opening 293 of plate 294 clamped against the end of casing 290 by a hollow cap 295. The return conduit 277 communicates with the hollow interior of cap 295.

It will be seen that bore 291 has an enlarged threaded portion 296 and that valve element 292 has a portion threadedly engaged therewith, whereby rotation of the valve element relative to the casing will shift the valve element toward and away from the valve seat to vary the size of opening 293. It will be apparent that if the valve element completely closes opening 293, the full pump pressure will be delivered to the assembly 222 to apply a maximum downward pull upon the boom. The pressure of the fluid delivered to assembly 222 to lower the boom will progressively diminish as the valve element is backed away from the seat, that is shifted to the left as viewed in Figure 16, since more and more fluid is thereby bypassed to the return conduit 277.

Since the effect of gravity causes the abrasive wheel to be urged downwardly against the work with a greater force in the out position of the boom, it is necessary to gradually reduce the pressure of the fluid delivered to assemby 222 to urge the boom downwardly as the boom moves out, or to the left in Figure 1, to account for the increasing effect of gravity.

As pointed out above, one of the principal reasons for employing assembly 222 as a hold down device for the boom is the fact that it is not feasible to completely and accurately counterbalance the boom by weights alone throughout its in and out movement so that the pressure of the wheel upon the work is uniform in all positions of axial movement of the boom. This is due in part, at least, to the fact that, in addition to the boom, 'a number of other parts, such as the various hydraulic and electric motors, move relative to the boom pivot axis which are practically impossible to accurately counter-balance. In the present instance, while the counterweight measurably reduces the weight of the abrasive wheel upon the work, still the wheel may bear against the work with 100 pounds more force in the extreme out position than in the extreme in position, due to gravity. In this instance, it is desirable to have the pull down device 222 add to the force of the wheel against the work by an'amount which is 100 pounds greater in the in" position than in the out position and which progressively varies between these positions.

riage 88, which supports the abrasive wheel motor and is, of course, movable in accordance with the axial movement of the boom, has a bracket 300 depending therefrom and secured to the upper reach of a cable 301. Cable 301 is trained over pulleys 302 mounted on the frame structure of carriage 12 and the cable also is trained over pulley 303 on gear box 304 supported on carriage 12. The output shaft 305 of the gear box has an annular disc 306 sleeved thereon, the disc having a hub portion axially adjustably secured to shaft 305 by a set screw 307. A circular disc 308 is secured to the outer end of valve element 292 which has a plurality of circumferentially spaced openings arranged in diametrically opposed relation in a circular array adjacent its periphery. As seen in Figure 16, a pair of pins 309 project from disc 306 and enter diametrically opposed open ings in disc 308 so that the valve element 292 is rotatable as a unit with shaft 305 of the gear box.

It will be apparent that as the boom moves along its axis between extreme in and out positions, that the valve element 292 will move toward or away from the seat to vary the pressure of fluid delivered to the upper end of the assembly 222. In the present instance, the valve element moves axially in a direction toward the valve seat, to increase the pressure of fluid delivered to the upper end of assembly 222, when the boom moves inwardlyor to the left in Figure 2, and the valve element moves away from the seat, to decrease the pressure of fluid delivered to the upper end of assembly 222, when the boom moves outwardly. There will be a gradual substantially straight-line variation in the pressure delivered to the assembly 222 by valve 286 as the boom moves axially.

Not only does the hold down assembly 222 make it possible to completely and accurately counterbalance the boom so the abrasive wheel bears upon the work with a constant pressure irrespective of the axial position of the boom, but chattering of the wheel on the work is eliminated. As pointed out above, even where the boom is counterbalanced to be tool heavy, there is a tendency to chatter where no positive resistance to upward swinging of the outer end of the boom is provided. It is apparent that in addition to the actual pull down pressure applied by assembly 222, the hydraulic fluid therein provides a positive resistance preventing upward swinging of the boom to eliminate chattering. This positive pressure resistance to upward swinging is much greater than the actual pull down pressure and is determined by the setting of the pressure-regulating valve 286. The valve 286 bypasses hydraulic fluid back to the reservoir at a rate determined by the size of the opening or metering orifice to maintain a predetermined downward pressure on the boom. It will be understood that if, for any reason, forces are encountered tending to raise the boom, as where irregularities in the work piece are encountered, or in instances Where the boom begins to chatter in a vertical plane, the body of hydraulic fluid in the hydraulic piston cylinder assembly 222 will positively resist any such upward movement. The magnitude of the forces set up by the body of hydraulic fluid will, of course, depend upon the size of the metering orifice 293 since this orifice provides an escape for the body of hydraulic fluid in the assembly 222. However, due to its small size, the rate to which it will release fluid from the as sembly 222 is likewise small and, accordingly, the pressures resisting upward movement of the boom are great. As pointed out, the actual resistance to upward swinging is determined by the setting of the pressure-regulating valve 286. The valve 286 may be very simply adjusted by mere loosening of set screw 307 and retracting disc 306 to withdraw pins 309 from the openings in disc 308. Then the boom may be moved inwardly or outwardly a predetermined distance and the disc 306 advanced to engage pins 309 in the aligned pair of openings in disc 308.

The operation of the machine will be readily apparent from the foregoing. The carriage 12 may be moved in opposite directions along track 10 by selective motion of valve 39 to position 2 or position 3. The boom may be oscillated or rocked about its longitudinal axis by the electric motor 266 having suitable controls available to the operator. The boom may be moved in and out along its axis by selective shifting of valve to position 2 or 3. Finally the outer end of the boom may be raised or lowered by operation of valve 232. In position 1 of valve 232, the boom is urged downwardly with a variable pressure determined by the perssure regulating valve 286. In position 2 of valve 232, the outer end of the boom is raised to move the abrasive wheel away from the work.

What I claim as my invention:

1. A machine for removing metal from a work piece comprising supporting structure, a boom mounted on the supporting structure for sliding movement along the longitudinal axis of said boom and pivoted intermediate its ends for vertical swinging movement, an abrasive wheel mounted on the outer end of said boom for engagement with a work piece supported therebeneath, means for moving said boom in opposite directions along its longitudinal axis to feed the abrasive wheel back and forth across the work piece, and means for maintaining said abrasive wheel against the work piece with a uniform pressure as it moves back and forth across the work piece comprising mechanism acting upon said boom for urging the outer end of said boom downwardly under a pressure which progressively decreases as said boom moves outwardly along its longitudinal axis and which progressively increases as said boom moves inwardly along its longitudinal axis, said mechanism comprising a fluid pressure device, and control means for determining the pressure applied upon said boom by said device operated by the movement of said boom along its longitudinal axis.

2. A machine as defined in claim 1 having means for supplying fluid under pressure to said device, said control means comprising a pressure regulating valve interposed between said fluid supplying means and said device.

3. A machine as defined in claim 2 including counterbalancing means for said boom mounted at the inner side of the pivoted mounting for sliding movement along the longitudinal axis of said boom, and means operable upon sliding movement of the boom in one direction for moving said counterbalancing means in the opposite direction relative to said boom.

4. A machine for removing metal from a work piece comprising a carriage supported for movement along a predetermined path of travel, supporting structure mounted on said carriage, a boom mounted on said supporting structure for sliding movement along the longitudinal axis of said boom and pivoted intermediate its ends for vertical swinging movement, an abrasive wheel mounted on the outer end of said boom for engagement with a work piece supported therebeneath, means for moving said boom in opposite directions along its longitudinal axis to feed said abrasive wheel back and forth across the work piece, and means for maintaining said abrasive wheel against the work piece with a uniform pressure as it moves back and forth across the work piece comprising mechanism acting upon said boom for urging the outer end thereof downwardly with a uniform pressure which progressively decreases as said boom moves outwardly along its longitudinal axis and which progressively increases as said boom moves inwardly along its longitudinal axis, said mechanism comprising a hydraulic fluid pressure device, and a control means for determining the pressure applied upon said boom by said device operated by the movement of said boom along its longitudinal axis.

5. A machine as defined in claim 4 having means for supplying hydraulic fluid under pressure to said device, said control means comprising a pressure regulating valve 1 1 interposed between said fluid supplying means and said device.

6. A machine as defined in claim 5 including counter balancing means for said boom mounted at the inner side of the pivoted mounting for sliding movement along the longitudinal axis of said boom, and means operable upon sliding movement of the boom in one direction for moving said counterbalancing means in the opposite direction relative to said boom.

7. A machine for removing metal from a work piece comprising a carriage supported for movement along a predetermined path of travel, supporting structure mounted on said carriage, a boom mounted on said supporting structure for sliding movement along the longitudinal axis of said boom and pivoted intermediate its ends for vertical swinging movement, an abrasive wheel mounted on the outer end of said boom for engagement with a work piece supported therebeneath, means for moving said boom in opposite directions along its longitudinal axis to feed said abrasive wheel back and forth across the work piece, and means for maintaining said abrasive wheel against the Work piece with a uniform pressure as it moves back'and forth across the work piece comprising a reversible hydraulic fluid pressure device operatively connected to said boom, means for supplying hydraulic fluid under pressure to said device to move said device in a direction to raise the outer end of said boom, means for supplying hydraulic fluid under pressure to said device to move the latter in a direction to lower the outer end of said boom, and control means for said last-named fluid supplying means operated by the axial movement of said boom for progressively decreasing the pressure of the fluid delivered to said device as said boom moves outwardly along its axis and for progressively increasing the pressure of the fluid delivered to said device as said boom moves inwardly along its axis.

8. A machine as defined in claim 7 in which said control means comprises an adjustable pressure regulating valve.

9. A machine as defined in claim 8 including counterbalancing means for said boom mounted at the inner side of the pivotal mounting for sliding movement along the longitudinal axis of said boom, and means operable upon sliding movement of the boom in one direction for moving said counterbalancing means in the opposite direction relative to said boom.

10. A machine for removing metal from a work piece comprising a carriage supported for movement along a predetermined path of travel, supporting structure mounted on said carriage, a boom mounted on said supporting structure for sliding movement along the longitudinal axis of said boom and pivoted intermediate its ends for vertical swinging movement, an abrasive wheel mounted on the outer end of said boom for engagement with a work piece supported therebeneath, means for moving said boom in opposite directions along its longitudinal axis to feed said abrasive wheel back and forth across the work piece, means for raising and lowering the outer end of said boom to move said abrasive wheel out of and into engagement with the work piece including a double acting hydraulic fluid pressure operated piston-cylinder assembly operatively connected to said boom, means for supplying hydraulic fluid under pressure to one end of said assembly to raise the outer end of said boom, means for supplying hydraulic fluid under pressure to the other end of said assembly to lower the outer end of said boom and to hold said abrasive wheel against the work piece under a predetermined pressure, and pressure regulating means associated with said last-mentioned means and operated by the movement of said boom along its longitudinal axis for progressively increasing the pressure of fluid delivered to said assembly as the boom moves inwardly along its longitudinal axis and for progressively decreasing the pressure of the fluid delivered to said assembly as the boom moves outwardly along its longitudinal axis, thereby to determine the pressure with which said abrasive wheel is held against the work piece.

ll. A machine as defined in claim 10 including counterbalancing means for said boom mounted at the inner side of the pivotal mounting for sliding movement along the longitudinal axis of said boom, and means operable upon sliding movement of the boom in one direction for moving said counterbalancing means in the opposite direction relative to said boom.

12. A machine for removing metal from a work piece comprising supporting structure, a boom housing, means pivotally mounting said housing on said supporting structure for vertical swinging movement, a boom supported on said housing, means mounting said boom on said housing for rotation and for sliding movement along its longitudinal axis, said boom projecting outwardly beyond the outer end of said housing, a metal removing tool on the outer end of said boom, means on the inner end porlast-named means comprises a motor having an output shaft, a part on said shaft disposed eccentric to the axis thereof, and a yoke secured to said member having spaced legs projecting transversely of said member, said part being received between the legs of said yoke.

14. A machine as defined in claim 13 in which said supporting structure comprises a carriage and a track along which said carriage is movable.

15. A machine for operating upon a work piece comprising supporting structure, a boom, means pivotally mounting said boom on said supporting structure for vertical swinging movement, a tool mounted on said boom at one side of the pivotal mounting means for engagement with a Work piece supported therebeneath, means for moving said tool in opposite directions along the longitudinal axis of said boom at said one side of said pivotal mounting means to feed said tool back and forth across the work piece, means for maintaining said tool against the work piece with a uniform pressure as it moves back and forth across the Work piece comprising mechanism acting upon said boom for urging the portion thereof at the said one side of said pivotal mounting means downwardly under a variable pressure, and control means for said mechanism operated in response to the movement of said tool along the longitudinal axis of said boom for progressively decreasing the downward pressure applied to said boom by said mechanism as said tool moves along the longitudinal axis of said boom away from said pivotal mounting means and for progressively increasing the downward pressure applied to said boom by said mechanism as said tool moves along the longitudinal axis of said boom toward said pivotal mounting means.

16. A machine as defined in claim 15, said mechanism comprising a fluid pressure device, means for supplying fluid under pressure to said device, and saidcontrol means comprisin a pressure regulating valve interposed between said fluid supplying means and said fluid pressure device.

17. A machine for removing metal from a work piece comprising supporting structure, a boom mounted on the supporting structure for sliding movement along the longitudinal axis of said boom and pivoted intermediate its ends for vertical swinging movement, an abrasive wheel mounted on the outer end of said boom for engagement With a work piece supported therebeneath, means for moving said boom in opposite d1rect1ons 310118 ngitudinal axis to feed the abrasive wheel back and forth across the work piece, and means for maintaining said abrasive wheel against the work piece with a uniform pressure as it 1' 1OV6S back and forth across the work piece comprising mechanism acting upon said boom for urging the outer end of said boom downwardly under a variable pressure, and control means for said mechanism operated by the movement of said boom along its longitudinal axis for progressively decreasing the downward pressure applied to said boom by said mechanism as said boom moves outwardly along its longitudinal axis and for progressively increasing the downward pressure applied to said boom by said mechanism as said boom moves inwardly along its longitudinal axis.

18. A machine for removing metal from a work piece comprising supporting structure, a boom mounted on the supporting structure for sliding movement along its longitudinal axis and pivoted for vertical swinging movement about an axis intermediate its ends, a metal removing tool mounted on said boom at the outer side of the pivot axis for engagement with a work piece supported therebeneath, counterbalancing means for said boom mounted at the inner side of the pivot axis for sliding movement along the longitudinal axis of said boom, a pair of rotatable members mounted in spaced relation axially of said boom, a flexible linear member reeved over said rotatable members, a part on said counterbalancing means secured to one reach of said linear member, and a part on said boom operatively connected to said linear member for moving said linear member in a direction such that movement of said boom along its longitudinal axis in one direction moves said counterbalancing means along the longitudinal axis of said boom in the opposite direction.

19. A machine for removing metal from a work piece comprising supporting structure, a boom, means mounting said boom on the supporting structure for vertical swinging movement about an axis intermediate the ends of said boom and for sliding movement along the longitudinal axis of said boom, a metal removing tool mounted upon said boom outwardly of said axis for engagement with a work piece supported therebeneath, a support rigid with said mounting means extending inwardly therefrom beyond the inner end of said boom, counterbalancing means supported on said support for sliding movement along the longitudinal axis of said boom, a first pair of rotatable members mounted on said support in spaced relation longitudinally of said boom, a flexible linear member over said rotatable members, a part on the inner end of said boom secured to one reach of said linear member, a second pair of rotatable members respectively axially aligned with the first pair, a second flexible linear member reeved over said second pair 14 of rotatable members, and a part on said counterbalancing means secured to one reach of said second linear member, such that movement of said boom along its longitudinal axis in one direction moves said counterbalancing means along the longitudinal axis of said boom in the opposite direction.

20. A machine as defined in claim 19 in which the supporting structure comprises a carriage and a track along which said carriage is' movable, and power means mounted on said carriage for propelling the same along said track.

21. A machine as defined in claim 19 having a reversible motor for moving said boom inwardly and outwardly along its longitudinal axis, and reversible means for swinging said boom about said axis to move the tool into and out of engagement with the work piece.

22. A machine for operating on a work piece comprising supporting structure, a boom mounted on said supporting structure for sliding movement along its longitudinal axis and for rotation about its longitudinal axis, a tool mounted on said boom and engageable with the Work piece, an elongated member at one end of said boom arranged coaxially therewith, means connecting said elongated member to said boom for rotation as a unit therewith and for sliding movement relative thereto along the longitudinal axis of said boom, and means for oscillating said member to impart a corresponding oscillating movement to said boom including a motor having an output shaft, a part on said shaft disposed eccentric to the axis thereof, and a yoke secured to said member having spaced legs projecting transversely of said member, said part being received between the legs of said yoke.

References Cited in the file of this patent UNITED STATES PATENTS 742,044 LOW Oct. 20, 1903 752,248 Nickerson Feb. 16, 1904 753,477 Drake Mar. 1, 1904 807,118 Kelly Dec. 12, 1905 1,321,983 Cole Nov. 18, 1919 1,427,799 Foulk Sept. 5, 1922 1,987,982 Wheeler Jan. 15, 1935 2,060,814 Lewis Nov. 17, 1936 2,200,274 Hayes May 14, 1940 2,262,049 Robinson Nov. 11, 1941 2,347,875 Bratz May 2, 1944 2,360,070 Meyerbach Oct. 10, 1944 2,442,042 Hamilton May 25, 1948 2,541,045 Ferwerda Feb. 13, 1951 2,694,274 McGibbon Nov. 16, 1954 2,708,378 Smith May 17, 1955 2,750,714 Muehling June 14, 1956 

